At present, a pair of “stereoscopic images” having “binocular parallax” can be controlled to enter a left eye and a right eye of a viewer by controlling a signal or by using an auxiliary device, and based on a principle of binocular parallax, the viewer can view a 3D stereoscopic image with the 3D effect, which is called the 3D displaying. The 3D displaying is mainly classified into a light-division type and a time-division type depending on the display principle. For the light-division type 3D displaying, for example, a phase retard 3D displaying, since a display screen displays left-eye and right-eye pictures at the same time, the brightness thereof is half of that of a 2D displaying mode.
A current liquid crystal display device can be switched between a 2D displaying mode and a 3D displaying mode, and however, it can only simply increase a brightness of a backlight source in the 3D displaying mode. Thus, such controlling manner to the backlight source is not flexible and can result in too high brightness in a 2D displaying mode.